The present invention relates to a hand tool such as a screwdriver or the like having a speed change gear train incorporated therein to provide the driving bit with higher angular speed than the handle. The present invention further incorporates a direct transmission gear to directly transmit torque to the driving bit without changing the rotational speed.
Conventionally, a screwdriver usually includes a shank integrated with a handle so that the rotation speed is the same for both the shank and the handle. This happens to be inefficient in loosening or tightening a long screw, because almost the whole screwing time is spent in rotating the screw with little torque but at the same low speed as the condition that great torque is required. It is, obviously, efficient to screw with a screwdriver which, instead of providing only the normal operational mode, further provides a high speed operation mode of which the rotational speed of the driving bit is much faster than the handle.